A social network typically comprises-a person's set of direct and indirect personal relationships. Direct personal relationships usually include relationships with family members, friends, colleagues, coworkers, and other people with which the person has had some form of direct contact, such as contact in person, by telephone, by email, by instant message, by letter, and the like. These direct personal relationships are sometimes referred to as first degree relationships. First degree relationships can have varying degrees of closeness, trust, and other characteristics. These relationships can also be unidirectional or bidirectional. A unidirectional relationship typically means that a first person is willing and able to interact with a second person, but the second person is not willing or able to interact with the first person. Conversely, a bidirectional relationship typically means that both people are willing and able to interact with each other.
Indirect personal relationships typically include relationships through first degree relationships to people with whom a person has not had some form of direct contact. For example, a friend of a friend represents an indirect personal relationship. A more extended, indirect relationship might be a friend of a friend of a friend. These indirect relationships are sometimes characterized by a degree of separation between the people. For instance, a friend of a friend can be characterized as a second degree relationship.